Absorbent articles with improved odor control

ABSTRACT

A technique for incorporating odor control agent particles into an absorbent article is provided. More specifically, the odor control particles are “homogenously” distributed (e.g., in a substantially uniform manner) within an airformed fiber matrix of an absorbent core of an absorbent article. An absorbent core containing such a homogeneously distributed odor control particles may possess a greater surface area for contacting malodorous compounds, thereby increasing the likelihood of odor reduction.

BACKGROUND OF THE INVENTION

Odor control agents have been incorporated into absorbent articles for avariety of reasons. For instance, U.S. Patent Application PublicationNo. 2003/0203009 to MacDonald describes an odor control agent that isformed from high surface area particles modified with a metal ion.Although such modified particles are effective in reducing odor,problems may nevertheless arise when attempting to incorporate the odorcontrol agents into an absorbent article. For example, it is oftendifficult to retain loose particles in the desired location forefficacious adsorption of odors from urine or other bodily fluids.Additionally, separate addition of odor control agents into absorbentarticles requires investment for capital equipment and results inincreased process complexity.

As such, a need currently exists for an improved technique forincorporating an odor control agent into an absorbent article.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, an absorbentarticle having odor control properties is disclosed. The articlecomprises an absorbent core that includes an airformed web, theairformed web containing a matrix of fluff pulp fibers in which ishomogeneously distributed odor control particles.

In accordance with another embodiment of the present invention, a methodfor forming an absorbent web with odor control properties is disclosed.The method comprises treating a fibrous sheet with a coating formulationthat comprises odor control particles; fiberizing the sheet to form aplurality of individual fibers; entraining the fibers in a gaseousstream; and thereafter, depositing the fibers onto a forming surface.

In accordance with still another embodiment of the present invention, amethod for forming an absorbent web with odor control properties isdisclosed. The method comprises treating a superabsorbent material witha coating formulation, the coating formulation comprising odor controlparticles; fiberizing a fibrous sheet to form a plurality of individualfibers; entraining the fibers in a gaseous stream; intermixing thetreated superabsorbent material with the entrained fibers; andthereafter, depositing the fibers and the treated superabsorbentmaterial onto a forming surface.

Other features and aspects of the present invention are discussed ingreater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth more particularly in the remainder of the specification, whichmakes reference to the appended figures in which:

FIG. 1 is a schematic view of one embodiment of a forming apparatus thatmay be used in the present invention; and

FIG. 2 illustrates a perspective view of an absorbent article that maybe formed according to one embodiment of the present invention.

Repeat use of reference characters in the present specification anddrawings is intended to represent same or analogous features or elementsof the invention.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

Reference now will be made in detail to various embodiments of theinvention, one or more examples of which are set forth below. Eachexample is provided by way of explanation, not limitation of theinvention. In fact, it will be apparent to those skilled in the art thatvarious modifications and variations may be made in the presentinvention without departing from the scope or spirit of the invention.For instance, features illustrated or described as part of oneembodiment, may be used on another embodiment to yield a still furtherembodiment. Thus, it is intended that the present invention cover suchmodifications and variations.

Generally speaking, the present invention is directed to a technique forincorporating odor control particles into an absorbent article. Morespecifically, the odor control particles are “homogenously” distributed(e.g., distributed in a substantially uniform manner) within anairformed fiber matrix of an absorbent core of an absorbent article. Anabsorbent core containing such a homogeneously distributed odor controlparticles may possess a greater surface area for contacting malodorouscompounds, thereby increasing the likelihood of odor reduction.

I. Odor Control Particles

Any of a variety of odor control particles may be used in accordancewith the present invention that are capable of imparting odor control toan absorbent article. For example, inorganic oxide particles, such assilica, alumina, zirconia, magnesium oxide, titanium dioxide, ironoxide, zinc oxide, copper oxide, zeolites, clays (e.g., smectite clay),combinations thereof, and so forth, may be employed in some embodimentsof the present invention. Various examples of such inorganic oxideparticles are described in U.S. Patent Application Publication Nos.2003/0203009 to MacDonald; 2005/0084412 to Macdonald, et al.;2005/0085144 to Macdonald, et al.; 2005/0084464 to McGrath, et al.;2005/0084474 to Wu, et al.; and 2005/0084438 to Do, et al., which areincorporated herein in their entirety by reference thereto for allpurposes.

The inorganic oxide particles may possess various forms, shapes, andsizes depending upon the desired result. For instance, the particles maybe in the shape of a sphere, crystal, rod, disk, tube, string, etc. Ifdesired, the particles may be relatively nonporous or solid. That is,the particles may have a pore volume that is less than about 0.5milliliters per gram (ml/g), in some embodiments less than about 0.4milliliters per gram, in some embodiments less than about 0.3 ml/g, andin some embodiments, from about 0.2 ml/g to about 0.3 ml/g. The averagesize of the particles is generally less than about 500 microns, in someembodiments less than about 100 microns, in some embodiments less thanabout 100 nanometers, in some embodiments from about 1 to about 50nanometers, in some embodiments from about 2 to about 50 nanometers, andin some embodiments, from about 4 to about 20 nanometers. As usedherein, the average size of a particle refers to its average length,width, height, and/or diameter. Further, the particles may also have ahigh surface area, such as from about 50 square meters per gram (m²/g)to about 1000 m²/g, in some embodiments from about 100 m²/g to about 600m²/g, and in some embodiments, from about 180 m²/g to about 240 m²/g.Surface area may be determined by the physical gas adsorption (B.E.T.)method of Bruanauer, Emmet, and Teller, Journal of American ChemicalSociety, Vol. 60, 1938, p. 309, with nitrogen as the adsorption gas.Without intending to be limited by theory, it is believed that particleshaving such a small size and high surface area may improve theadsorption capability for many malodorous compounds. Moreover, it isbelieved that the solid nature, i.e., low pore volume, of the particlesmay enhance the uniformity and stability of the particles, withoutsacrificing their odor adsorption characteristics.

The “zeta potential” of the particles may also vary as desired. Forexample, the particles may possess a negative zeta potential, such asless than about 0 millivolts (mV), in some embodiments less than about−10 mV, and in some embodiments, less than about −20 mV. Commerciallyavailable examples of particles having a negative zeta potential includeSnowtex-C, Snowtex-O, Snowtex-PS, and Snowtex-OXS, which are silicananoparticles available from Nissan Chemical of Houston, Tex.Alternatively, the particles may have a zeta potential of greater thanabout +20 millivolts (mV), in some embodiments greater than about +30mV, and in some embodiments, greater than about +40 mV. By possessing apositive surface charge, the particles are well suited for being affixedto fibers that carry a negative surface charge (e.g., cellulosic fibers)through ionic attraction. Depending upon the difference in chargebetween the particles and the surface of the fibers (including van derWaals forces), the bond in some applications may be relatively permanentand substantive. Consequently, the particles may be affixed to fiberswithout the use of chemical binders or other attachment structures.

A positive zeta potential may be imparted to the particles of thepresent invention in a variety of different ways. In one embodiment, theparticles are formed entirely from a positively charged material. Forexample, alumina particles may be used for odor reduction in accordancewith the present invention. Some suitable alumina particles aredescribed in U.S. Pat. No. 5,407,600 to Ando. et al., which isincorporated herein in its entirety by reference thereto for allpurposes. Further, examples of commercially available alumina particlesinclude, for instance, Aluminasol 100, Aluminasol 200, and Aluminasol520, which are available from Nissan Chemical Industries Ltd.Alternatively, the positive zeta potential may be imparted by acontinuous or discontinuous coating present on the surface of a corematerial. In some instances, these particles may actually possess abetter stability over various pH ranges than particles formed entirelyfrom positively charged materials. In one particular embodiment, forexample, the particles are formed from silica particles coated withalumina. A commercially available example of such alumina-coated silicaparticles is Snowtex-AK, which is available from Nissan Chemical ofHouston, Tex.

The inorganic oxide particles may also be modified with one or moretransition metals to improve their odor control properties. Morespecifically, without being limited by theory, it is believed that thetransition metal provides one or more active sites for capturing and/orneutralizing a malodorous compound. The active sites may be free, or maybe weakly bound by water molecules or other ligands so that they arereplaced by a malodorous molecule when contacted therewith. In addition,the particles still have the large surface area that is useful inadsorbing other malodorous compounds. Examples of some suitabletransition metals that may be used in the present invention include, butare not limited to, scandium, titanium, vanadium, chromium, manganese,iron, cobalt, nickel, copper, zinc, silver, gold, and so forth. Singlemetallic, as well as dinuclear, trinuclear, and cluster systems may beused.

The transition metal may be applied to the particles in a variety ofways. For instance, particles may simply be mixed with a solutioncontaining the appropriate transition metal in the form of a salt, suchas those containing a copper ion (Cu⁺²), silver ion (Ag⁺), gold ion (Au⁺and Au⁺³), iron (II) ion (Fe⁺²), iron (III) ion (Fe⁺³), and so forth.Such solutions are generally made by dissolving a metallic compound in asolvent resulting in free metal ions in the solution. Generally, themetal ions are drawn to and adsorbed onto the particles due to theirelectric potential differences, i.e., they form an “ionic” bond. In manyinstances, however, it is desired to further increase the strength ofthe bond formed between the metal and particles, e.g., to form acoordinate and/or covalent bond. Although ionic bonding may still occur,the presence of coordinate or covalent bonding may have a variety ofbenefits, such as reducing the likelihood that any of the metal willremain free during use (e.g., after washing). Further, a strongadherence of the metal to the particles also optimizes odor adsorptioneffectiveness.

If desired, more than one type of transition metal may be bound to aparticle. This has an advantage in that certain metals may be better atremoving specific malodorous compounds than other metals. Likewise,different types of modified particles may be used in combination foreffective removal of various malodorous compounds. In one embodiment,for instance, copper-modified silica particles are used in combinationwith manganese-modified silica particles. By using two differentmodified particles in combination, numerous malodorous compounds may bemore effectively removed. For example, the copper-modified particle maybe more effective in removing sulfur and amine odors, while themanganese-modified particle may be more effective in removing carboxylicacids. The ratio of the transition metal to the particles may beselectively varied to achieve the desired results. In most embodiments,for example, the mole ratio of the transition metal to the particles isat least about 10:1, in some embodiments at least about 50:1, and insome embodiments, at least about 100:1.

In addition to inorganic oxide particles, other particulate odor controlagents may be employed in the present invention. For example, a quinonepowder having odor control characteristics may also be used in thepresent invention. Quinone powders may be prepared by drying a quinonecompound in an oven and then converting the dried material to a powderusing a milling device, such as a ball mill, bead mill, vibratory mill,sand mill, colloid mill, etc. Suitable dispersing agents may be, forexample, condensation products of naphthalene sulfonic acid andformaldehyde, lignosulfonates or nonionic and anionic surface-activecompounds. The resulting powder generally has an average particle sizeof from about 0.01 microns to about 20 microns, in some embodiments fromabout 0.5 microns to about 10 microns, and in some embodiments, fromabout 0.03 microns to about 6 microns. As used herein, the average sizeof a particle refers to its average length, width, height, and/ordiameter. Some suitable anthraquinone powders are commercially availablefrom Noveon Hilton Davis, Inc. of Cincinnati, Ohio and Sigma-AldrichChemical Co., Inc. of St. Louis, Mo.

Generally speaking, quinones refer to a class of compounds that possessa quinoid ring, such as anthraquinones, naphthaquinones, benzoquinones,hydroquinones, and so forth. Anthraquinones, for instance, have thefollowing general formula:

The numbers 1-8 shown in the general formula represent a location on thefused ring structure at which substitution of a functional group mayoccur. Some examples of such functional groups that may be substitutedon the fused ring structure include halogen groups (e.g., chlorine orbromine groups), sulfonyl groups (e.g., sulfonic acid salts), alkylgroups, benzyl groups, amino groups (e.g., primary, secondary, tertiary,or quaternary amines), carboxy groups, cyano groups, hydroxy groups,phosphorous groups, etc. Functional groups that result in an ionizingcapability are often referred to as “chromophores.” Substitution of thering structure with a chromophore causes a shift in the absorbancewavelength of the compound. Thus, depending on the type of chromophore(e.g., hydroxyl, carboxyl, amino, etc.) and the extent of substitution,a wide variety of quinones may be formed with varying colors andintensities. Other functional groups, such as sulfonic acids, may alsobe used to render certain types of compounds (e.g., higher molecularweight anthraquinones) water-soluble.

Anthraquinone compounds may be classified for identification by theirColor Index (CI) number, which is sometimes called a “standard.” Forinstance, some suitable anthraquinones that may be used in the presentinvention, as classified by their “CI” number, include Acid Black 48,Acid Blue 25 (D&C Green No. 5), Acid Blue 40, Acid Blue 41, Acid Blue45, Acid Blue 80, Acid Blue 129, Acid Green 25, Acid Green 27, AcidGreen 41, Acid Violet 43, Mordant Red 11 (Alizarin), Mordant Black 13(Alizarin Blue Black B), Mordant Red 3 (Alizarin Red S), Mordant Violet5 (Alizarin Violet 3R), Alizarin Complexone, Natural Red 4 (CarminicAcid), Disperse Blue 1, Disperse Blue 3, Disperse Blue 14, Natural Red16 (Purpurin), Natural Red 8, Reactive Blue 2 (Procion Blue HB),Reactive Blue 19 (Remazol Brilliant Blue R); and so forth. Thestructures of Acid Blue 25, Acid Green 41, Acid Blue 45, Mordant Violet5, Acid Blue 129, Acid Green 25, and Acid Green 27 are set forth below:

As stated above, other quinones may also be used in the presentinvention. For example, naphthaquinones may be used that have thefollowing general formula:

The locations 1-6 of the naphthaquinone compounds may be substitutedwith functional groups in the manner described above. For instance,suitable examples of naphthaquinone compounds that may be used in thepresent invention include 1,4 naphthaquinone and 1,2 naphthaquinone,which have the following structures:

Without intending to be limited by theory, it is believed that the odorcaused by many compounds is eliminated by the transfer of electrons toand/or from the malodorous compound. Specifically, oxidation ofmalodorous compounds via a reduction/oxidation (“redox”) reaction isbelieved to inhibit the production of the characteristic odor associatedtherewith. The discovery that certain quinone compounds are able toeliminate odor is believed to be due to their ability to function as anoxidizing agent in a redox reaction. Many common malodorous compounds(e.g., ethyl mercaptan) are capable of being oxidized (i.e., donateelectrons) via a redox reaction. Upon oxidation, the odors associatedwith such compounds are often eliminated or at least lessened. It isalso believed that the reduction of the quinone compound via the redoxreaction is readily reversible, and thus the reduced quinone compoundmay be oxidized by any known oxidizing agent (e.g., oxygen, air, etc.).The reduction/oxidation reactions are rapid and may take place at roomtemperature. Thus, although the odor control mechanism may consume thequinone compounds, they may simply be regenerated by exposure to air.Thus, long-term odor control may be achieved without significantlyaffecting the ability of the quinone compound to impart the desiredcolor.

In addition to their ability to oxidize malodorous compounds, thechemical structure of certain quinone compounds may help improve odorelimination. For example, anthraquinone compounds that have at least oneunsubstituted ring may result in better odor inhibition than those thatare substituted at each ring with a functional group. Interestingly,anthraquinone compounds that are unsubstituted at the “first” ring(i.e., positions 5 through 8) appear to be particularly effective inreducing odor. Suitable examples of anthraquinone compounds that areunsubstituted at locations at their first ring include, but are notlimited to, Acid Blue 25, Acid Blue 129, Acid Green 25, and Acid Green27, the structures of which are set forth above. Other exemplary odorcontrol quinone compounds are described in U.S. Patent ApplicationPublication No. 2005/0131363 to Macdonald, et al., which is incorporatedherein in its entirety by reference thereto for all purposes.

In the embodiments described above, the odor control agent inherentlypossesses a particulate form to increase the surface area available forcontact with malodorous compounds and to facilitate fiber application.In some cases, however, the odor control particles may be formed bypre-treating carrier particles with an odor control agent. For example,carrier particles may be treated with quinone compounds, such asdescribed above. Although not required, the carrier particles may alsohave odor control properties. In one embodiment, for instance, thecarrier particles may be inorganic oxide particles. Superabsorbentparticles may also serve as useful carrier particles. Superabsorbentparticles are water-swellable materials capable of absorbing at leastabout 20 times its weight and, in some cases, at least about 30 timesits weight in an aqueous solution containing 0.9 weight percent sodiumchloride. The superabsorbent particles may be natural, synthetic andmodified natural polymers and materials. Examples of syntheticsuperabsorbent material polymers include the alkali metal and ammoniumsalts of poly(acrylic acid) and poly(methacrylic acid),poly(acrylamides), poly(vinyl ethers), maleic anhydride copolymers withvinyl ethers and alpha-olefins, poly(vinyl pyrrolidone),poly(vinylmorpholinone), poly(vinyl alcohol), and mixtures andcopolymers thereof. Further superabsorbent materials include natural andmodified natural polymers, such as hydrolyzed acrylonitrile-graftedstarch, acrylic acid grafted starch, methyl cellulose, chitosan,carboxymethyl cellulose, hydroxypropyl cellulose, and the natural gums,such as alginates, xanthan gum, locust bean gum and so forth. Mixturesof natural and wholly or partially synthetic superabsorbent polymers mayalso be useful in the present invention. Particularly suitablesuperabsorbent polymers are HYSORB 8800AD (BASF of Charlotte, N.C. andFAVOR SXM 9300 (available from Degussa Superabsorber of Greensboro,N.C.).

Regardless of the particular odor control particles employed, they maybe dispersed in a solvent to form a coating formulation that is thenapplied to the fibers. Any solvent capable of dispersing or dissolvingthe components is suitable, such as water; alcohols, such as ethanol ormethanol; dimethylformamide; dimethyl sulfoxide; hydrocarbons, such aspentane, butane, heptane, hexane, toluene and xylene; ethers such asdiethyl ether and tetrahydrofuran; ketones and aldehydes, such asacetone and methyl ethyl ketone; acids, such as acetic acid and formicacid; and halogenated solvents, such as dichloromethane and carbontetrachloride; as well as mixtures thereof. The concentration of solventin the coating formulation is generally high enough to allow aneconomically feasible application process. If the amount of solvent istoo large, however, the amount of odor control particles might be toolow to provide the desired odor reduction. Although the actualconcentration of solvent employed will generally depend on the type ofodor control particles and the fibers to which they are applied, theyare nonetheless typically present in an amount from about 40 wt. % toabout 99 wt. %, in some embodiments from about 65 to about 98 wt. %, andin some embodiments, from about 80 wt. % to about 96 wt. % of thecoating formulation. The amount of the odor control particles added tothe coating formulation will vary depending on the amount of odorreduction desired and the maximum concentration that may be dispersed ordissolved in the coating solution. For example, the odor controlparticles may constitute from about 0.01 wt. % to about 20 wt. %, insome embodiments from about 0.1 wt. % to about 15 wt. %, and in someembodiments, from about 0.5 wt. % to about 10 wt. % of the coatingformulation. The solids content of the coating formulation may also bevaried to achieve the extent of odor reduction desired. For example, thecoating formulation may have a solids content of from about 1% to about60%, in some embodiments from about 2% to about 35%, and in someembodiments, from about 4% to about 20%. By varying the solids contentof the formulation, the presence of the odor control particles may becontrolled. For example, to form a coating formulation with a higherlevel of odor control particles, the formulation may be provided with arelatively high solids content so that a greater percentage of theparticles are incorporated into the formulation during the applicationprocess.

II. Fiber Treatment

As noted above, the odor control particles of the present invention maybe homogeneously distributed within a matrix of fibers, such ashydrophilic fibers, used to form the absorbent core of an absorbentarticle. Hydrophilic fibers may include natural and/or synthetic fluffpulp fibers. The fluff pulp fibers may be kraft pulp, sulfite pulp,thermomechanical pulp, etc. In addition, the fluff pulp fibers mayinclude high-average fiber length pulp, low-average fiber length pulp,or mixtures of the same. One example of suitable high-average lengthfluff pulp fibers includes softwood kraft pulp fibers. Softwood kraftpulp fibers are derived from coniferous trees and include pulp fiberssuch as, but not limited to, northern, western, and southern softwoodspecies, including redwood, red cedar, hemlock, Douglas-fir, true firs,pine (e.g., southern pines), spruce (e.g., black spruce), combinationsthereof, and so forth. Northern softwood kraft pulp fibers may be usedin the present invention. One example of commercially available southernsoftwood kraft pulp fibers suitable for use in the present inventioninclude those available from Weyerhaeuser Company with offices inFederal Way, Wash. under the trade designation of “NB-416.” Anothersuitable fluff pulp for use in the present invention is a bleached,sulfate wood pulp containing primarily softwood fibers that is availablefrom Bowater Corp. with offices in Greenville, S.C. under the trade nameCoosAbsorb S pulp. Low-average length fibers may also be used in thepresent invention. An example of suitable low-average length pulp fibersis hardwood kraft pulp fibers. Hardwood kraft pulp fibers are derivedfrom deciduous trees and include pulp fibers such as, but not limitedto, eucalyptus, maple, birch, aspen, etc. Eucalyptus kraft pulp fibersmay be particularly desired to increase softness, enhance brightness,increase opacity, and change the pore structure of the sheet to increaseits wicking ability.

In addition, synthetic fibers may also be utilized. Some suitablepolymers that may be used to form the synthetic fibers include, but arenot limited to: polyolefins, such as, polyethylene, polypropylene,polybutylene, and so forth; polyesters, such as polyethyleneterephthalate, poly(glycolic acid) (PGA), poly(lactic acid) (PLA),poly(β-malic acid) (PM LA), poly(ε-caprolactone) (PCL),poly(p-dioxanone) (PDS), poly(3-hydroxybutyrate) (PHB), and so forth;and, polyamides, such as nylon and so forth. Synthetic or naturalcellulosic polymers, including but not limited to, cellulosic esters;cellulosic ethers; cellulosic nitrates; cellulosic acetates; cellulosicacetate butyrates; ethyl cellulose; regenerated celluloses, such asviscose, rayon, and so forth. Non-wood fibers may also be used,including fiber originating from hemp, straw, flax, bagasse, andmixtures thereof may be used in the present invention.

To homogeneously distribute the odor control particles within the matrixof fibers, any of a variety of application techniques may be employed.For example, the odor control particles may be topically applied to adry lap sheet of fluff pulp. The dry lap sheet may then be subjected toa fiberizing process that breaks the sheet into a plurality ofindividual fibers. These individual fibers may then be supplied to aforming chamber that deposits the fibers onto a foraminous surface toform an airformed web. Due to the vigorous mixing imparted by thefiberizing process, the odor control particles thus become homogeneouslydistributed throughout the web structure. Additionally, a superabsorbentmaterial that is pre-coated with an odor control agent may be separatelyinjected into the forming chamber where it will mix with the fibers.

Various specific embodiments of the aforementioned techniques will nowbe described in greater detail. It should be understood, however, thatthe embodiments described are merely exemplary, and that various otherembodiments are also contemplated by the present invention. In thisregard, referring to FIG. 1, one embodiment of a forming apparatus 20that may be used in the present invention is depicted. As shown, theapparatus 20 includes a fiberizer 44, such as a rotary hammermill,rotatable picker roll, or any other conventional fiberizing device. Adry lap sheet 80 of fluff pulp is supplied to the fiberizer 44 to form aplurality of individual fibers. In one embodiment of the presentinvention, the dry lap sheet is pre-treated with odor control particlesusing conventional techniques, such as printing, dipping, spraying, meltextruding, solvent coating, powder coating, and so forth. The percentcoverage and add-on level of the odor control particles may beselectively varied to achieve any desired distribution within the finalweb. For instance, the percent coverage of the odor control particlesmay be greater than about 50%, in some embodiments greater than about80%, and in some embodiments, approximately 100% of the area of a givensurface. Likewise, the odor control particles are typically applied inan amount from about 0.01 wt. % to about 20 wt. %, in some embodimentsfrom about 0.1 wt. % to about 10 wt. %, and in some embodiments, fromabout 1 wt. % to about 5 wt. % based on the weight of pulp fibers.

Once fiberized, the individual fibers are entrained in a stream of agaseous medium (e.g., air), and then ejected or otherwise introducedinto a forming chamber 32. Although illustrated below the fiberizer 44,the forming chamber 32 may also be positioned at any other location,such as to the side or at a remote location that is spaced away from thefiberizer 44. The forming chamber 32 may direct and concentrate thegas-entrained fibers and provide a desired velocity profile in thestream. Various suitable forming chamber configurations are described,for instance, in U.S. Pat. No. 4,927,582 to Bryson and U.S. Pat. No.6,630,096 to Venturino, et al., which are incorporated herein in theirentirety by reference thereto for all purposes.

The apparatus 20 also includes a movable, foraminous forming surface 22onto which a fibrous web 50 is formed. Typically, the forming surface 22is provided by a foraminous, air permeable material, such as a wireforming cloth, screen, perforated plate, fabric, belt, drum, etc.Suitable forming belts are commercially available from the PaperConverting Machine Co. of Green Bay, Wis. and from Curt G. Joa, Inc. ofSheboygan Falls, Wis. In the illustrated embodiment, the forming surface22 is provided by a forming drum 40. During use, the forming drum 40 isrotated in a desired direction by a drum drive shaft (not shown) that isoperatively joined to a drive mechanism (not shown). The drive mechanismmay include an electric or other motor that is directly or indirectlycoupled to the drive shaft. If desired, the forming surface 22 mayinclude a series of separately removable, forming sections that aredistributed circumferentially along the periphery of the forming drum40. Such forming sections may optionally provide a selected repeatpattern that is formed in the resulting fibrous web. The repeat patternmay correspond to a desired shape of an individual absorbent pad that isintended for assembly or other placement in an absorbent article.Suitable forming drum systems are described in more detail in U.S. Pat.No. 4,666,647 to Enloe, et al.; U.S. Pat. No. 4,761,258 to Enloe; andU.S. Pat. No. 6,330,735 to Hahn, et al., which are incorporated hereinin their entirety by reference thereto for all purposes.

The interior space of the forming drum 40 may include a vacuum zonehaving the general form of an arcuate segment located at the portion ofthe forming surface 22 positioned within the forming chamber 32. In theillustrated embodiment, for instance, the vacuum zone is locatedadjacent to the forming chamber 32 and may include features provided bya vacuum duct 24. The portion of the forming drum 40 positioned withinthe boundaries of the forming chamber 32 may delimit or otherwiseprovide a lay-down zone of the forming surface 22. Such a vacuumlay-down zone may, for example, constitute a circumferential,cylindrical surface portion of the rotatable drum 40. A pressuredifferential is imposed on the surface of the vacuum lay-down zone by aconventional vacuum source (e.g., vacuum pump, an exhaust blower, etc.)to provide a relatively low pressure under the forming surface 22. Underthe influence of the vacuum source, a conveying gas stream is thus drawnthrough the forming surface 22 into the interior of the forming drum 40,and subsequently passed out of the drum through a vacuum supply conduit42. As the gas-entrained fibers impinge on the foraminous formingsurface 22, a gas (e.g., air) is passed through the forming surface 22to cause the fibers to be retained on the surface to form a fibrous web50.

If desired, drum rotation may then pass the fibrous web 50 to a scarfingzone where excess thickness may be trimmed and removed to apredetermined extent. More specifically, the scarfing system may includea scarfing chamber 48 and a scarfing roll 46 positioned therein. Thescarfing roll 46 rotates in a direction opposite to the movementdirection of the laid fibrous web 50. Alternatively, the scarfing roll46 may be rotated to provide a co-directional movement of the rollersurface relative to the surface of the forming drum proximate thereto.In either case, the rotational speed of the scarfing roll 46 is selectedto provide an effective scarfing action against the contacted surface ofthe formed fibrous web 50 to abrade excess fibrous material therefrom.If desired, the removed fibrous material may be recycled back into theforming chamber 32 or the fiberizer 44, as desired. Additionally, thescarfing roll 46 may rearrange and redistribute the web material alongthe longitudinal machine-direction of the web and/or along the lateralcross-direction of the web.

After the scarfing operation, the portion of the forming surface 22 thatis carrying the fibrous web 50 may be moved to an optional pressureblow-off zone of the forming drum system. In the blow-off zone, a gas(e.g., air) may be introduced under pressure and directed radiallyoutwardly against the fibrous web on the portion of the forming surfacethat becomes aligned with the blow-off zone. The gas pressure may causethe fibrous web to release from the forming surface 22 onto a suitableweb transport mechanism. The web transporter may receive the fibrous web50 from the forming drum 40 and convey it for further processing.Suitable web transporters may include conveyer belts, vacuum drums,transport rollers, electromagnetic suspension conveyors, fluidsuspension conveyors or the like, as well as combinations thereof. Asshown, for instance, the web transporter may include a conveyor belt 52disposed about rollers 53. In a particular embodiment, a vacuum suctionbox 122 is located below the conveyor belt 52 to help remove the web 50from the forming surface 22. The vacuum box 122 opens onto the belt 52and draws gas through perforations in the conveyor belt 52. In turn,this flow of gas draws the web 50 away from the forming surface 22. Thevacuum box 122 may be employed with or without the use of a positivepressure in the blow-off zone. The removed fibrous web 50 may provide aninterconnected series of pads, and each pad may have a selected surfacecontour that substantially matches the contour provided by the various,corresponding portions of the forming surface 22 upon which eachindividual pad was formed.

It will be readily apparent that various conventional devices andtechniques may be employed to further process the web 50. For example,various conventional devices and techniques may be employed to severfibrous web 50 into predetermined lengths to provide selected laidfibrous articles. The severing system may, for example, include a diecutter, a water cutter, a rotary knives, reciprocating knives, energybeam cutters, particle beam cutters or the like, as well as combinationsthereof. After severing, the discrete fibrous pads 50 may be transportedand delivered for further processing operations.

In addition to or on in conjunction with being pre-treated onto a drylap sheet, the odor control particles may also be applied substantiallyconcurrently with the formation of the web. For example, odor controlparticles may be pre-coated onto a superabsorbent material and thenintroduced into the forming chamber 32. The amount of odor controlparticles applied to the superabsorbent material may generally vary toachieve the desired effect. For example, the odor control particles maybe applied in an amount from about 0.01% to about 20% by weight, in someembodiments from about 0.1% to about 10% by weight, and in someembodiments, from about 0.5% to about 5% by weight of the superabsorbentmaterial. Thereafter, the treated superabsorbent material may then bedelivered into the forming chamber 32. Upon intermixing with the fibers,the odor control particles may thus become homogeneously distributedwithin the resulting fibrous web 50. Additionally, both fibers andsuperabsorbents treated with odor control particles could be placed in afibrous web. In such cases, the odor control particles may be the sameor different.

The superabsorbent material (optionally pre-coated with the odor controlparticles) may be introduced into the forming chamber 32 usingconventional mechanisms, such as pipes, channels, spreaders, nozzles andso forth, as well as combinations thereof. In the illustratedembodiment, for example, the apparatus 20 may include a nozzle 54 thatdispenses the odor control particles into the forming chamber 32. Thenozzle 54 may be any conventional component of a spraying system, suchas a hydraulic spray system, air atomizing spray system, ultra-sonicspray system and so forth. In desired arrangements, a flat-pattern spraynozzle may be used in which the longest dimension of the spray patternis aligned generally along the cross-direction of the apparatus. Asuitable flat-pattern spray nozzle is a UNIJET® spray nozzle availablefrom the Spraying Systems Co. of Wheaton Ill. In particulararrangements, the spray nozzle may have a spray orifice diameter that iswithin the range of about 0.25 to 2.5 millimeters.

The spray nozzle 54 may be placed a certain distance above the formingsurface 22, with the distance being measured along a straight referenceline that intersects the center of the outlet orifice of the nozzle 54and extends perpendicular to the forming surface 22 at the localposition of the spray nozzle 54. The distance may be selectively variedto achieve the desired results. If the distance is too small, thespraying process may excessively interfere with the formation of theabsorbent web and increase the likelihood of plugging in the nozzle. Onthe other hand, if the distance is too large, it may be difficult tomaintain the desired distribution stream of the odor control particlesfrom the nozzle. Thus, the distance is typically from about 10millimeters to about 250 millimeters, in some embodiments from about 40millimeters to about 200 millimeters, and in some embodiments, fromabout 80 millimeters to about 150 millimeters.

When applied to fluff pulp, the odor control particles typicallyconstitute from about 0.01 wt. % to about 25 wt. %, in some embodimentsfrom about 0.1 wt. % to about 15 wt. %, and in some embodiments, fromabout 0.5 wt. % to about 10 wt. % of the treated fluff pulp fibers. Thetreated fluff pulp fibers may also be blended with untreated fluff pulpfibers or other fibers, polymers, or superabsorbent material to form thefibrous web. In such cases, the percentage of treated pulp fibers mayrange from about 5 wt. % to about 100 wt. %, in some embodiments fromabout 10 wt. % to about 100 wt. %, and in some embodiments, from about10 wt. % to about 90 wt. % of the fibrous web. The total amount of odorcontrol particles in the fibrous web may likewise range from about 0.01wt. % to about 20 wt. %, in some embodiments from about 0.1 wt. % toabout 10 wt. %, and in some embodiments, from about 0.5 wt. % to about 5wt. % of the web. Superabsorbent content may range from 0% up to about90% of the fibrous web.

III. Absorbent Articles

When formed in accordance with the present invention, the resultingfibrous web contains odor control particles that are capable of reducingor inhibiting one or more odors. In addition, due to their homogeneousdistribution within the web, the odor control particles are better ableto contact malodorous compounds over the entire surface of the web. Suchan odor-reducing web may be used in a wide variety of applications. Inone particular embodiment, for example, the fibrous web may be used inan absorbent article. An “absorbent article” generally refers to anyarticle capable of absorbing water or other fluids. Examples of someabsorbent articles include, but are not limited to, personal careabsorbent articles, such as diapers, training pants, absorbentunderpants, incontinence articles, feminine hygiene products (e.g.,sanitary napkins), swim wear, baby wipes, and so forth; medicalabsorbent articles, such as garments, fenestration materials, underpads,bedpads, bandages, absorbent drapes, and medical wipes; food servicewipers; clothing articles; and so forth. Materials and processessuitable for forming such absorbent articles are well known to thoseskilled in the art. Typically, absorbent articles include asubstantially liquid-impermeable layer (e.g., outer cover), aliquid-permeable layer (e.g., bodyside liner, surge layer, etc.), and anabsorbent core. The treated fibrous web of the present invention may beemployed as any one or more of the liquid transmissive (non-retentive)and absorbent layers, and is desirably used to form the absorbent core.For example, the treated fibrous web may form the entire absorbent core.Alternatively, the treated fibrous web may form only a portion of thecore, such as a layer of an absorbent composite that includes one ormore additional layers (e.g., wet-formed paper webs, coform webs, etc.).Regardless, the odor control particles contained within the fibrous webmay contact malodorous compounds absorbed by the absorbent core (e.g.,urine) and thereby reduce the amount of odor released by the article.

Various embodiments of an absorbent article that may be formed accordingto the present invention will now be described in more detail. Forpurposes of illustration only, an absorbent article is shown in FIG. 2as a diaper 1. However, as noted above, the invention may be embodied inother types of absorbent articles, such as incontinence articles,sanitary napkins, diaper pants, feminine napkins, children's trainingpants, and so forth. In the illustrated embodiment, the diaper 1 isshown as having an hourglass shape in an unfastened configuration.However, other shapes may of course be utilized, such as a generallyrectangular shape, T-shape, or I-shape. As shown, the diaper 1 includesa chassis 2 formed by various components, including an outer cover 17,bodyside liner 5, absorbent core 3, and surge layer 7. It should beunderstood, however, that other layers may also be used in the presentinvention. Likewise, one or more of the layers referred to in FIG. 2 mayalso be eliminated in certain embodiments of the present invention.

The outer cover 17 is typically formed from a material that issubstantially impermeable to liquids. For example, the outer cover 17may be formed from a thin plastic film or other flexibleliquid-impermeable material. In one embodiment, the outer cover 17 isformed from a polyethylene film having a thickness of from about 0.01millimeter to about 0.05 millimeter. If a more cloth-like feeling isdesired, the outer cover 17 may be formed from a polyolefin filmlaminated to a nonwoven web. For example, a stretch-thinnedpolypropylene film having a thickness of about 0.015 millimeter may bethermally laminated to a spunbond web of polypropylene fibers. Thepolypropylene fibers may have a denier per filament of about 1.5 to 2.5,and the nonwoven web may have a basis weight of about 17 grams persquare meter. The outer cover 17 may also include bicomponent fibers,such as polyethylene/polypropylene bicomponent fibers. In addition, theouter cover 17 may also contain a material that is impermeable toliquids, but permeable to gases and water vapor (i.e., “breathable”).This permits vapors to escape from the absorbent core 3, but stillprevents liquid exudates from passing through the outer cover 17.

The diaper 1 also includes a bodyside liner 5. The bodyside liner 5 isgenerally employed to help isolate the wearer's skin from liquids heldin the absorbent core 3. For example, the liner 5 presents a bodyfacingsurface that is typically compliant, soft feeling, and non-irritating tothe wearer's skin. Typically, the liner 5 is also less hydrophilic thanthe absorbent core 3 so that its surface remains relatively dry to thewearer. The liner 5 may be liquid-permeable to permit liquid to readilypenetrate through its thickness. The bodyside liner 5 may be formed froma wide variety of materials, such as porous foams, reticulated foams,apertured plastic films, natural fibers (e.g., wood or cotton fibers),synthetic fibers (e.g., polyester or polypropylene fibers), or acombination thereof. In some embodiments, woven and/or nonwoven fabricsare used for the liner 5. For example, the bodyside liner 5 may beformed from a meltblown or spunbonded web of polyolefin fibers. Theliner 5 may also be a bonded-carded web of natural and/or syntheticfibers. The liner 5 may further be composed of a substantiallyhydrophobic material that is optionally treated with a surfactant orotherwise processed to impart a desired level of wettability andhydrophilicity. The surfactant may be applied by any conventionalmethod, such as spraying, printing, brush coating, foaming, and soforth. When utilized, the surfactant may be applied to the entire liner5 or may be selectively applied to particular sections of the liner 5,such as to the medial section along the longitudinal centerline of thediaper. The liner 5 may further include a composition that is configuredto transfer to the wearer's skin for improving skin health. Suitablecompositions for use on the liner 5 are described in U.S. Pat. No.6,149,934 to Krzysik et al., which is incorporated herein in itsentirety by reference thereto for all purposes.

As illustrated in FIG. 2, the diaper 1 may also include a surge layer 7that helps to decelerate and diffuse surges or gushes of liquid that maybe rapidly introduced into the absorbent core 3. Desirably, the surgelayer 7 rapidly accepts and temporarily holds the liquid prior toreleasing it into the storage or retention portions of the absorbentcore 3. In the illustrated embodiment, for example, the surge layer 7 isinterposed between an inwardly facing surface 16 of the bodyside liner 5and the absorbent core 3. Alternatively, the surge layer 7 may belocated on an outwardly facing surface 18 of the bodyside liner 5. Thesurge layer 7 is typically constructed from highly liquid-permeablematerials. Suitable materials may include porous woven materials, porousnonwoven materials, and apertured films. Some examples include, withoutlimitation, flexible porous sheets of polyolefin fibers, such aspolypropylene, polyethylene or polyester fibers; webs of spunbondedpolypropylene, polyethylene or polyester fibers; webs of rayon fibers;bonded carded webs of synthetic or natural fibers or combinationsthereof. Other examples of suitable surge layers 7 are described in U.S.Pat. No. 5,486,166 to Ellis, et al. and U.S. Pat. No. 5,490,846 toEllis, et al., which are incorporated herein in their entirety byreference thereto for all purposes.

Besides the above-mentioned components, the diaper 1 may also containvarious other components as is known in the art. For example, the diaper1 may also contain a substantially hydrophilic tissue wrapsheet (notillustrated) that helps maintain the integrity of the fibrous structureof the absorbent core 3. The tissue wrapsheet is typically placed aboutthe absorbent core 3 over at least the two major facing surfacesthereof, and composed of an absorbent cellulosic material, such ascreped wadding or a high wet-strength tissue. The tissue wrapsheet maybe configured to provide a wicking layer that helps to rapidlydistribute liquid over the mass of absorbent fibers of the absorbentcore 3. The wrapsheet material on one side of the absorbent fibrous massmay be bonded to the wrapsheet located on the opposite side of thefibrous mass to effectively entrap the absorbent core 3.

Furthermore, the diaper 1 may also include a ventilation layer (notshown) that is positioned between the absorbent core 3 and the outercover 17. When utilized, the ventilation layer may help insulate theouter cover 17 from the absorbent core 3, thereby reducing dampness inthe outer cover 17. Examples of such ventilation layers may includebreathable laminates (e.g., nonwoven web laminated to a breathablefilm), such as described in U.S. Pat. No. 6,663,611 to Blaney, et al.,which is incorporated herein in its entirety by reference thereto forall purpose.

In some embodiments, the diaper 1 may also include a pair of ears (notshown) that extend from the side edges 32 of the diaper 1 into one ofthe waist regions. The ears may be integrally formed with a selecteddiaper component. For example, the ears may be integrally formed withthe outer cover 17 or from the material employed to provide the topsurface. In alternative configurations, the ears may be provided bymembers connected and assembled to the outer cover 17, the top surface,between the outer cover 17 and top surface, or in various otherconfigurations.

As representatively illustrated in FIG. 2, the diaper 1 may also includea pair of containment flaps 12 that are configured to provide a barrierand to contain the lateral flow of body exudates. The containment flaps12 may be located along the laterally opposed side edges 32 of thebodyside liner 5 adjacent the side edges of the absorbent core 3. Thecontainment flaps 12 may extend longitudinally along the entire lengthof the absorbent core 3, or may only extend partially along the lengthof the absorbent core 3. When the containment flaps 12 are shorter inlength than the absorbent core 3, they may be selectively positionedanywhere along the side edges 32 of diaper 1 in a crotch region 10. Inone embodiment, the containment flaps 12 extend along the entire lengthof the absorbent core 3 to better contain the body exudates. Suchcontainment flaps 12 are generally well known to those skilled in theart. For example, suitable constructions and arrangements for thecontainment flaps 12 are described in U.S. Pat. No. 4,704,116 to Enloe,which is incorporated herein in its entirety by reference thereto forall purposes.

The diaper 1 may include various elastic or stretchable materials, suchas a pair of leg elastic members 6 affixed to the side edges 32 tofurther prevent leakage of body exudates and to support the absorbentcore 3. In addition, a pair of waist elastic members 8 may be affixed tolongitudinally opposed waist edges 15 of the diaper 1. The leg elasticmembers 6 and the waist elastic members 8 are generally adapted toclosely fit about the legs and waist of the wearer in use to maintain apositive, contacting relationship with the wearer and to effectivelyreduce or eliminate the leakage of body exudates from the diaper 1. Asused herein, the terms “elastic” and “stretchable” include any materialthat may be stretched and return to its original shape when relaxed.Suitable polymers for forming such materials include, but are notlimited to, block copolymers of polystyrene, polyisoprene andpolybutadiene; copolymers of ethylene, natural rubbers and urethanes;etc. Particularly suitable are styrene-butadiene block copolymers soldby Kraton Polymers of Houston, Tex. under the trade name Kraton®. Othersuitable polymers include copolymers of ethylene, including withoutlimitation ethylene vinyl acetate, ethylene methyl acrylate, ethyleneethyl acrylate, ethylene acrylic acid, stretchable ethylene-propylenecopolymers, and combinations thereof. Also suitable are coextrudedcomposites of the foregoing, and elastomeric staple integratedcomposites where staple fibers of polypropylene, polyester, cotton andother materials are integrated into an elastomeric meltblown web.Certain elastomeric single-site or metallocene-catalyzed olefin polymersand copolymers are also suitable for the side panels.

The diaper 1 may also include one or more fasteners 30. For example, twoflexible fasteners 30 are illustrated in FIG. 2 on opposite side edgesof waist regions to create a waist opening and a pair of leg openingsabout the wearer. The shape of the fasteners 30 may generally vary, butmay include, for instance, generally rectangular shapes, square shapes,circular shapes, triangular shapes, oval shapes, linear shapes, and soforth. The fasteners may include, for instance, a hook material. In oneparticular embodiment, each fastener 30 includes a separate piece ofhook material affixed to the inside surface of a flexible backing.

The various regions and/or components of the diaper 1 may be assembledtogether using any known attachment mechanism, such as adhesive,ultrasonic, thermal bonds, etc. Suitable adhesives may include, forinstance, hot melt adhesives, pressure-sensitive adhesives, and soforth. When utilized, the adhesive may be applied as a uniform layer, apatterned layer, a sprayed pattern, or any of separate lines, swirls ordots. In the illustrated embodiment, for example, the outer cover 17 andbodyside liner 5 are assembled to each other and to the absorbent core 3using an adhesive. Alternatively, the absorbent core 3 may be connectedto the outer cover 17 using conventional fasteners, such as buttons,hook and loop type fasteners, adhesive tape fasteners, and so forth.Similarly, other diaper components, such as the leg elastic members 6,waist elastic members 8 and fasteners 30, may also be assembled into thediaper 1 using any attachment mechanism.

Although various configurations of a diaper have been described above,it should be understood that other diaper and absorbent articleconfigurations are also included within the scope of the presentinvention. For instance, other suitable diaper configurations aredescribed in U.S. Pat. No. 4,798,603 to Meyer et al.; U.S. Pat. No.5,176,668 to Bemardin; U.S. Pat. No. 5,176,672 to Bruemmer et al.; U.S.Pat. No. 5,192,606 to Proxmire et al.; and U.S. Pat. No. 5,509,915 toHanson et al., as well as U.S. Patent Application Pub. No. 2003/120253to Wentzel, et al., all of which are incorporated herein in theirentirety by reference thereto for all purposes. In addition, the presentinvention is by no means limited to diapers. In fact, any otherabsorbent article may be formed in accordance with the presentinvention, including, but not limited to, other personal care absorbentarticles, such as training pants, absorbent underpants, adultincontinence products, feminine hygiene products (e.g., sanitarynapkins), swim wear, baby wipes, and so forth; medical absorbentarticles, such as garments, fenestration materials, underpads, bandages,absorbent drapes, and medical wipes; food service wipers; clothingarticles; and so forth. Several examples of such absorbent articles aredescribed in U.S. Pat. No. 5,197,959 to Buell; U.S. Pat. No. 5,085,654to Buell; U.S. Pat. No. 5,634,916 to Lavon, et al.; U.S. Pat. No.5,569,234 to Buell, et al.; U.S. Pat. No. 5,716,349 to Taylor, et al.;U.S. Pat. No. 4,950,264 to Osborn, III; U.S. Pat No. 5,009,653 toOsborn, III; U.S. Pat. No. 5,509,914 to Osborn, III; U.S. Pat. No.5,649,916 to DiPalma, et al.; U.S. Pat. No.5,267,992 to Van Tillburg;U.S. Pat. No. 4,687,478 to Van Tillburg; U.S. Pat. No. 4,285,343 toMcNair; U.S. Pat. No. 4,608,047 to Mattingly; U.S. Pat. No. 5,342,342 toKitaoka; U.S. Pat. No. 5,190,563 to Herron, et al.; U.S. Pat. No.5,702,378 to Widlund, et al.; U.S. Pat. No. 5,308,346 to Sneller. etal.; U.S. Pat. No. 6,110,158 to Kielpikowski; U.S. Pat. No. 6,663,611 toBlaney. et al.; and WO 99/00093 to Patterson. et al., which areincorporated herein in their entirety by reference thereto for allpurposes. Still other suitable articles are described in U.S. PatentApplication Publication No. 2004/0060112 Al to Fell et al., as well asU.S. Pat. No. 4,886,512 to Damico et al.; U.S. Pat. No. 5,558,659 toSherrod et al.; U.S. Pat. No. 6,888,044 to Fell et al.; and U.S. Pat.No. 6,511,465 to Freiburger et al., all of which are incorporated hereinin their entirety by reference thereto for all purposes. The odorcontrol particles may also be placed on fibers that are formed into awet formed absorbent composite as described in U.S. Pat. No. 6,706,945to Melius et al. Further, the odor control particles may also beincorporated into elastomeric absorbent composites, such as thosedescribed in U.S. Pat. No. 6,582,413 to Krautkramer, et al., which isincorporated herein in its entirety by reference thereto for allpurposes.

The effectiveness of the odor control particles of the present inventionmay be measured in a variety of ways. For example, the percent of amalodorous compound adsorbed by the odor control particles may bedetermined in accordance with the headspace gas chromatography test setforth herein. In some embodiments, the odor control particles of thepresent invention are capable of adsorbing at least about 1%, in someembodiments at least about 2%, and in some embodiments, at least about5% of a particular malodorous compound, such as mercaptans (e.g., ethylmercaptan), ammonia, amines (e.g., trimethylamine (TMA), triethylamine(TEA), etc.), sulfides (e.g., hydrogen sulfide, dimethyl disulfide(DMDS), etc.), ketones (e.g., 2-butanone, 2-pentanone, 4-heptanone,etc.) carboxylic acids (e.g., isovaleric acid, acetic acid, propionicacid, etc.), aldehydes, terpenoids, hexanol, heptanal, pyridine, and soforth. It should be recognized that the surface chemistry of any onetype of odor control particles may not be suitable to reduce all typesof malodorous compounds, and that low adsorption of one or moremalodorous compounds may be compensated by good adsorption of othermalodorous compounds.

The present invention may be better understood with reference to thefollowing examples.

Test Methods

Quantitative and qualitative odor tests were used in the Examples.Quantitative odor adsorption was determined in the Examples using a testknown as “Headspace Gas Chromatography.” Headspace gas chromatographytesting was conducted on an Agilent Technologies 5890, Series II gaschromatograph with an Agilent Technology 7694 headspace sampler (AgilentTechnologies, Waldbronn, Germany). Helium was used as the carrier gas(injection port pressure: 87.5 kPa; headspace vial pressure: 108.9 kPa;supply line pressure is at 413.4 kPa). A DB-624 column was used for themalodorous compound that had a length of 30 meters and an internaldiameter of 0.25 millimeters. Such a column is available from J&WScientific, Inc. of Folsom, Calif.

The operating parameters used for the headspace gas chromatography areshown below in Table 1:

TABLE 1 Operating Parameters for the Headspace Gas ChromatographyDevice. Headspace Parameters Zone Temps, ° C. Oven 37 Loop 85 TR. Line90 Event Time, minutes GC Cycle time 10.0 Vial eq. Time 10.0 Pressuriz.Time 0.20 Loop fill time 0.20 Loop eq. Time 0.15 Inject time 0.30 VialParameters First vial 1 Last vial 1 Shake [off]

The test procedure involved placing approximately 5 milligrams of theodor control agent in a 22.1-cubic centimeter headspace vial. Using asyringe, an aliquot of the malodorous compound was also placed in thevial. Testing was done with 2.014 micrograms of ethyl mercaptan (2.4microliters) and 2.178 micrograms (3 microliters) of triethylamine(TEA). Each sample was tested in triplicate. The vial was then sealedwith a cap and a septum and placed in the headspace gas chromatographyoven at 37° C. After two (2) hours, a hollow needle was inserted throughthe septum and into the vial. A 1-cubic centimeter sample of theheadspace (air inside the vial) was then injected into the gaschromatograph. Initially, a control vial with only the aliquot ofmalodorous compound was tested to define 0% malodorous compoundadsorption. To calculate the amount of headspace malodorous compoundremoved by the sample, the peak area for the malodorous compound fromthe vial with the sample was compared to the peak area from themalodorous compound control vial.

Qualitative odor reduction was also assessed against urine odor.

EXAMPLE 1

Modified silica particles were prepared for treatment of a pulpsheet.The silica particles were Snowtex-OXS, which are colloidal silicananoparticles commercially available from Nissan Chemical America ofHouston, Tex. The particles have an average particle size of between 4to 6 nanometers and a surface area between 200 to 500 square meters pergram as measured using the BET (Brunauer, Emmett and Teller) method. Thesilica particles were modified with a transition metal as follows. Asolution of Snowtex-OXS (324 grams SiO₂, 3.62×10⁻³ moles SiO₂ particle,about 3 liters of Snowtex-OXS stock solution) was diluted with asolution of NaHCO₃ (13.44 grams NaHCO₃ in 500 milliliters water, 0.04molar final concentration for 4 liters) until the pH was about 8. Asolution of iron (III) chloride hexahydrate (FeCl₃.6H₂O) (97.9 grams,0.362 moles) in water (500 milliliters) was added to the Snowtex-OXSsolution via an addition funnel with vigorous stirring. The final silicaconcentration was 7.5% wt/wt. The iron-coated silica particle solutionturned light orange after the addition of the metal salt and was stirredat room temperature for 2 hours.

EXAMPLE 2

NB-416 southern softwood pulpsheet (available from Weyerhaeuser Co. ofFederal Way, Wash.) was treated with the particle solution of Example 1.Specifically, the solution was sprayed onto both sides of NB-416pulpsheet to attain 45.9 milligrams iron-coated silica particles pergram of pulp. The treated pulpsheet was dried at 50° C. overnight. Thetreated pulpsheet was then fiberized using a Kamas LaboratoryHammermill, Model H-01 pulp fiberizer to form fluff pulp.

EXAMPLE 3

Modified silica particles were prepared for treatment of asuperabsorbent material. The silica particles were Snowtex-OXS, whichare colloidal silica nanoparticles commercially available from NissanChemical America of Houston, Tex. The particles have an average particlesize of between 4 to 6 nanometers and a surface area between 200 to 500square meters per gram. The silica particles were modified with atransition metal as follows. A solution of Snowtex-OXS (216 grams SiO₂,2.41×10⁻³ moles SiO₂ particle, ˜2 liters of Snowtex-OXS stock solution)was diluted with a solution of NaHCO₃ (13.44 g NaHCO3 in 1 liter, 0.04molar final concentration for 4 liters) until the pH was about 8. Asolution of iron (III) chloride hexahydrate (FeCl₃.6H₂O) (65.25 grams,0.241 moles) in water (1 liter) was added to the OXS solution via anaddition funnel with vigorous stirring. The final silica concentrationwas 5% wt/wt. The iron coated silica particle solution turned lightorange after the addition of the metal salt and stirred at roomtemperature for 2 hours.

EXAMPLE 4

Hysorb® 8800AD superabsorbent (available from BASF of Charlotte, N.C.)was treated with the particle solution of Example 3. Specifically, sixhundred (600) grams of the solution was added to a one gallon Hobart®mixer, Model N50, manufactured by Hobart Canada of Ontario, Canada. Onehundred fifty (150) grams of distilled water was then added to themixer. The mixer was stirred at a slow speed (setting 1). Five hundred(500) grams dry Hysorb® 8800AD superabsorbent particles were added tothe mixer while stirring. After stirring for about 30 seconds, theswollen superabsorbent was discharged into a stainless steel pan (25.4cm×50.8 cm or 10 inches×20 inches). The treated superabsorbent was thendried in an oven at 60° C. for three days to attain 60 milligrams ofiron-coated silica particles per gram of superabsorbent.Non-agglomerated treated superabsorbent particles were separated fortesting by sieving to attain particle sizes of 150 microns to 850microns.

EXAMPLE 5

Hysorb® 8800AD superabsorbent (available from BASF of Charlotte, N.C.)was treated with the particle solution of Example 3. Specifically, fourhundred sixty (460) grams of the solution was added to a one gallonHobart® mixer. Two hundred ninety (290) grams of distilled water wasadded to the mixer. The mixer was stirred at a slow speed (setting 1).Five hundred (500) grams dry Hysorb® 8800AD superabsorbent particleswere added to the mixer while the stirrer was on. After stirring forabout 30 seconds, the swollen superabsorbent was discharged into astainless steel pan (25.4 cm×50.8 cm or 10 inches×20 inches). Thetreated superabsorbent was dried in an oven at 60° C. for three days toattain 45.9 milligrams iron coated silica particles per gram ofsuperabsorbent. Non-agglomerated treated superabsorbent particles wereseparated for testing by sieving to attain particle sizes of 150 micronsto 850 microns.

EXAMPLE 6

Weyerhaeuser NB-416 pulpsheet was treated with Acid Green 25, ananthraquinone-based Drug & Cosmetic approved dye available fromSigma-Aldrich of St. Louis, Mo. To form the Acid Green 25 solution,water (4 liters) was added to a 4 liter bottle, after which Acid Green25 (40 grams, 0.0642 moles) was added. The final Acid Green 25concentration was 1% wt/wt. Acid Green 25 solution was sprayed onto bothsides of NB-416 pulpsheet to attain 16.5 milligrams Acid Green 25 pergram of pulp. The treated pulpsheet was dried at 50° C. overnight. Thetreated pulpsheet was then fiberized using a Kamas LaboratoryHammermill, Model H-01 pulp fiberizer to form fluff pulp.

EXAMPLE 7

Modified silica particles were prepared. The silica particles wereSnowtex-AK, which are colloidal silica nanoparticles commerciallyavailable from Nissan Chemical America of Houston, Tex. The particleshave an average particle size of between 10 to 20 nanometers and asurface area between 200 to 500 square meters per gram. The silicaparticles were modified with Acid Green 25 as follows. Water (3.733liters) was added to a 4 liter bottle, after which Acid Green 25 (40grams) was added. The solution was shaken vigorously to affectdissolution, followed by addition of Snowtex-AK particles (267 ml, ˜15wt % in water initially) to generate a final solution concentration of1% wt/wt Snowtex-AK.

EXAMPLE 8

Weyerhaeuser NB-416 pulpsheet was treated with the solution of Example 7by spraying it onto both sides of the pulpsheet to attain 29.4milligrams Acid Green 25 coated silica particles per gram of pulp. Thetreated pulpsheet was dried at 50° C. overnight. The treated pulpsheetwas then fiberized using a Kamas Laboratory Hammermill, Model H-01 pulpfiberizer to form fluff pulp.

EXAMPLE 9

The effectiveness of the treated pulpsheet and superabsorbent to adsorbmalodorous compounds was demonstrated. The materials of Examples 2, 4,5, 6, and 8 were tested for odor adsorption as described above. Forcomparative purposes, untreated fiberized NB-416 fluff pulp and Hysorb8800AD superabsorbent were also tested. The results are set forth belowin Tables 2 and 3 in terms of milligrams of the malodorous compoundremoved per gram of sample, i.e., relative adsorption efficiency.

TABLE 2 Removal of Triethylamine Relative Adsorption Sample EfficiencyHysorb ® 8800AD −0.40 Iron/OXS treated Hysorb ® 8800AD from Ex. 4 3.80Iron/OXS treated Hysorb ® 8800AD from Ex. 5 3.00 NB-416 fluff pulp 0.74Iron/OXS treated NB-416 from Ex. 2 15.20 Acid Green 25 treated NB-416from Ex. 6 1.10 AG 25/AK treated NB-416 from Ex. 8 2.30

TABLE 3 Removal of Ethyl Mercaptan Relative Adsorption Sample EfficiencyHysorb ® 8800AD −0.80 Iron/OXS treated Hysorb ® 8800AD from Ex. 4 0.20Iron/OXS treated Hysorb ® 8800AD from Ex. 5 −0.10 NB-416 fluff pulp 0.58Iron/OXS treated NB-416 from Ex. 2 1.30 Acid Green 25 treated NB-416from Ex. 6 0.20 AG 25/AK treated NB-416 from Ex. 8 1.50

As indicated, improved odor control was observed in comparison withuntreated pulp and superabsorbent materials. The effect was strongerwith triethylamine than with ethyl mercaptan.

EXAMPLE 10

Fluff pulp and superabsorbent were homogeneously air-formed intoabsorbent composites. The formed absorbent composites were thencompressed using a Beloit Wheeler Model 700 debulking unit. Thematerials produced are shown below in Table 4.

TABLE 4 Airformed Absorbent Composites Super- Super- absorbent Pulpabsorbent Density Pulp type Superabsorbent % g/m² g/m² (g/cm³) NB-416Hysorb ® 8800AD 27 398 147 0.12 NB-416 Hysorb ® 8800AD 50 193 193 0.24NB-416 Iron/OXS treated 27 398 147 0.12 Hysorb ® 8800AD from Ex. 4NB-416 Iron/OXS treated 50 193 193 0.24 Hysorb ® 8800AD from Ex. 5Treated Hysorb ® 8800AD 50 193 193 0.24 NB-416 from Ex. 2 TreatedHysorb ® 8800AD 50 193 193 0.24 NB-416 from Ex. 8

EXAMPLE 11

The effectiveness of the treated pulpsheet and superabsorbent to adsorbmalodorous compounds when converted into an air-formed absorbentcomposite was demonstrated. The materials of Example 10 were tested forodor adsorption as described above. The results are set forth in Tables5 and 6 in terms of milligrams of the malodorous compound removed pergram of sample, i.e., relative adsorption efficiency.

TABLE 5 Removal of Triethylamine Super- Relative absorbent AdsorptionPulp type Superabsorbent % Efficiency NB-416 Hysorb ® 8800AD 27 1.21NB-416 Hysorb ® 8800AD 50 1.11 NB-416 Iron/OXS treated 27 2.94 Hysorb ®8800AD from Ex. 4 NB-416 Iron/OXS treated 50 2.70 Hysorb ® 8800AD fromEx. 5 Iron/OXS treated Hysorb ® 8800AD 50 4.12 NB-416 from Ex. 2 AG25/AK treated Hysorb ® 8800AD 50 1.73 NB-416 from Ex. 8

TABLE 6 Removal of Ethyl Mercaptan Super- Relative absorbent AdsorptionPulp type Superabsorbent % Efficiency NB-416 Hysorb ® 8800AD 27 0.12NB-416 Hysorb ® 8800AD 50 −0.05 NB-416 Iron/OXS treated 27 0.13 Hysorb ®8800AD from Ex. 4 NB-416 Iron/OXS treated 50 0.06 Hysorb ® 8800AD fromEx. 5 Iron/OXS treated Hysorb ® 8800AD 50 0.25 NB-416 from Ex. 2 AG25/AK treated Hysorb ® 8800AD 50 0.05 NB-416 from Ex. 8

As indicated, improved odor control was observed in comparison withuntreated pulp and superabsorbent materials.

EXAMPLE 12

To determine the potential for urine odor reduction, 76 mm (3 inch)diameter circles of the absorbent composites of Example 10 were insultedwith 10 milliliters of pooled female urine that had been incubated at37° C. for 6 hours and then filtered using a polyethersulfone (PES)membrane available from Corning of Acton, Mass. The materials were thenincubated at 37° C. for 1 hour in 1-qt screw top mason jars beforeassessment. Four panelists rated the pads on a scale of 1 to 10 forurine odor, with lower numbers signifying low urine odor and highnumbers signifying high urine odor. The results are shown below in Table7.

TABLE 7 Urine Odor Control Rankings Super- Pulp Super- absorbentPanelist Panelist Panelist Panelist type absorbent % 1 2 3 4 NB-416Hysorb ® 27 9 8 10 8 8800AD NB-416 Hysorb 50 10 8 7 7 8800AD NB-416Iron/OXS 27 4 8 5 1 treated Hysorb ® 8800AD from Ex. 4 NB-416 Iron/OXS50 4 8 3 2 treated Hysorb ® 8800AD from Ex. 5 Treated Hysorb ® 50 1 1 12 NB-416 8800AD from Ex. 2 Treated Hysorb ® 50 5 10 3 10 NB-416 8800ADfrom Ex. 8

As indicated, decreased urine odor was observed in comparison withuntreated pulp and superabsorbent materials.

While the invention has been described in detail with respect to thespecific embodiments thereof, it will be appreciated that those skilledin the art, upon attaining an understanding of the foregoing, mayreadily conceive of alterations to, variations of, and equivalents tothese embodiments. Accordingly, the scope of the present inventionshould be assessed as that of the appended claims and any equivalentsthereto.

1. A method for forming an absorbent web with odor control properties,the method comprising: treating a fibrous sheet with a coatingformulation that comprises odor control particles; fiberizing thetreated sheet to form a plurality of individual fibers; entraining thefibers in a gaseous stream; and thereafter, depositing the fibers onto aforming surface to form a web comprising odor control particles, whereinsubstantially all of the odor control particles in the web originatefrom the treated sheet.
 2. The method of claim 1, wherein the odorcontrol particles are inorganic oxide particles.
 3. The method of claim2, wherein the inorganic oxide particles contain silica, alumina, orboth.
 4. The method of claim 3, wherein the inorganic oxide particlesare modified with a transition metal.
 5. The method of claim 1, whereinthe odor control particles contain a quinone compound.
 6. The method ofclaim 1, wherein the odor control particles constitute from about 0.01to about 20 wt. % of the coating formulation.
 7. The method of claim 1,wherein a solvent constitutes from about 40 to about 99 wt. % of thecoating formulation.
 8. The method of claim 1, wherein the odor controlparticles are homogeneously distributed within the web.
 9. The method ofclaim 1, wherein the odor control particles are present in an amount offrom about 0.1 to about 10 wt. % of the web.
 10. The method of claim 1,wherein the fibrous sheet is a fluff pulp sheet.
 11. A method forforming an absorbent web with odor control properties, the methodcomprising: treating a superabsorbent material with a coatingformulation, the coating formulation comprising odor control particles;fiberizing a fibrous sheet to form a plurality of individual fibers;entraining the fibers in a gaseous stream; intermixing substantially allof the treated superabsorbent material with the entrained fibers; andthereafter, depositing the fibers and the treated superabsorbentmaterial onto a forming surface to form a web comprising odor controlparticles, wherein substantially all of the odor control particles inthe web originate from the treated superabsorbent material.
 12. Themethod of claim 11, wherein the odor control particles are inorganicoxide particles.
 13. The method of claim 12, wherein the inorganic oxideparticles contain silica, alumina, or both.
 14. The method of claim 13,wherein the inorganic oxide particles are modified with a transitionmetal.
 15. The method of claim 11, wherein the odor control particlescontain a quinone compound.
 16. The method of claim 11, wherein the odorcontrol particles constitute from about 0.01 to about 20 wt. % of thecoating formulation.
 17. The method of claim 11, wherein a solventconstitutes from about 40 to about 99 wt. % of the coating formulation.18. The method of claim 1, wherein the odor control particles arehomogeneously distributed within the web.
 19. The method of claim 11,wherein the odor control particles are present in an amount of fromabout 0.1 to about 10 wt. % of the web.
 20. The method of claim 11,wherein the fibrous sheet is a fluff pulp sheet.